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Physical Geography A-level > Classification of mass movements > Flashcards

Classification of mass movements Flashcards

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1
Q

Mass movement is when…

A

rock/earth falls/slides/flows due to gravity.

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2
Q

Flow is triggered when the composition…

A

of soil/rock is disrupted. The particles near the surface are disrupted more.

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3
Q

Flow is a non-

A

uniform movement.

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4
Q

(flow) Saturated topsoil results in…

A

lose of hydrostatic pressure and cohesion. The material eventually slips/flow.

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5
Q

After slip/flow, new…

A

deeper particles are exposed and start to lubricate.

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6
Q

A slide is a uniform…

A

movement.

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7
Q

During the process of formation of a slide, no internal…

A

disruption to rock and its properties takes place. Topsoil is disrupted.

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8
Q

The slide is caused by water…

A

sitting between the topsoil and already saturated bedrock. This creates a slip plane and the topsoil slides.

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9
Q

Heave is…

A

a very slow mass movement.

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10
Q

Heave is mainly occurring during…

A

winter.

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11
Q

Heave occurs on slopes with gradient…

A

5 degrees or more that have very little vegetation cover, which bind the soil.

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12
Q

Heave is caused by water…

A

particles in the soil, which expand as they freeze by 9 per cent.

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13
Q

As the water expands in the soil…

A

the soil is pushed 90 degrees to the slope, as it is the zone of least resistance for particles to expand.

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14
Q

The particles fall under a influcence of…

A

gravity, when the frozen water thawed and returned to its original shape.

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15
Q

As this freeze-thaw of water particles in soil repeats…

A

there is a net movement down the slope.

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16
Q

Rainsplash is a type of…

A

soil erosion caused from the impact of raindrops.

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17
Q

The impact of rain droplets on the soil surface often…

A

separate individual grains of soil moving them further from their source.

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18
Q

On flat surface, there is no effect of…

A

rainsplash erosion as the material is distributed without any net transport and particular direction.

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19
Q

(rain splash)On slopes, the influence of…

A

gravity encourages more material to be redistributed down the slope.

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20
Q

When slopes become steeper than…

A

25 degrees, almost all the redistribution occurs down the slope.

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21
Q

Surface wash happens when…

A

the soil’s infiltration capacity is exceeded.

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22
Q

Surface wash is common in…

A

winter as water drains across saturated or frozen ground and in semi-arid regions where particle size limits the infiltration.

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23
Q

Sheet wash is…

A

an unhandled flow of water over the soil.

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24
Q

Sheetwash usually breaks into areas of…

A

higher and lower velocities.

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25
Q

The higher velocities areas may cause…

A

gullying, which is the formation of narrow channel(rills)

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26
Q

Sheetwash may transport…

A

the surface regolith such as material dislodged by rain splash.

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27
Q

In semi-arid areas, the sheet wash can lower…

A

the surfaces by 2-5mm per year compared to 0.01mm on vegetated slopes.

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28
Q

Heave is continual…

A

process.

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29
Q

Soil creep is a slow…

A

movement of soil particles down the slope.

30
Q

Talus creep is…

A

slow movement of scree fragments down the slope.

31
Q

Exposed roots of three up…

A

slope is evidence of soil creep.

32
Q

Evidence of soil creep:

A

Stress fractures in buildings and fractured roads/pavements

33
Q

Trees react to…

A

the soil creep by bending the tree trunk.

34
Q

Falls occur on steep slopes greater than…

A

40 degrees, especially on bare rock surfaces.

35
Q

Initial causes of fall may be…

A

chemical or physical weathering, which reduces the sheer strength of the rock.

36
Q

Short falls produce relatively…

A

straight screes-talus slopes

37
Q

Talus is…

A

as the pile of rocks that accumulates at the base of a cliff or slope.

38
Q

Longer falls produce…

A

a concave scar.

39
Q

Falls are significant in…

A

producing the retreat of steep rock faces.

40
Q

Slip plane of slides occurs along…

A

a fault line, between two different layers, a joint or a bendding plane.

41
Q

Clay is particlulary vulnerable to…

A

the development of slip planes.

42
Q

More water on the slope…

A

increases the water pressure and pushes particles apart, which reduces strength. It also lubricates the slope.

43
Q

Slumps occur in…

A

a weaker rocks, especially finely weathered clays.

44
Q

Slumps have a rotational…

A

movement along a curved slip plane.

45
Q

Slumps are likely to occur when…

A

material becomes saturated with water and gains wight.

46
Q

Often, before slumps, the base of…

A

the cliff is undercut by erosion(waves).

47
Q

Rotational slumps are marked by…

A

a tilting back of the slumped mass which will expose a steep curved scar behind and pushes out a toe at the front.

48
Q

Flows are more continous and less…

A

jerky than slumps. They have a higher water content, so more fluid.

49
Q

Types of flows:

A
  • solifluction
  • debris/earth flow
  • mudflow
50
Q

Solifluction is the slowest…

A

form of flow. Around 10cm per year on the surface.

51
Q

Solifluction is common in…

A

cold climates where frozen ground limits percolation and occur on gentle slopes (5-15 degrees).

52
Q

Solifluction is formed as…

A

regolith becomes saturated with water. The lubricated layer then moves down the slope.

53
Q

Features of the solifluction are…

A

lobes, which are rounded tongue like features that can be up to 50m wide.

54
Q

Earth/debris flow occurs on slopes…

A

5-15 degrees.

55
Q

Earth/debris flow is thicker than…

A

mudflow due to lower water content.

56
Q

Earth/debris flow is caused by…

A

a rapid input of water from either rain or snowmelt, which causes a slippage.

57
Q

Earth/debris flow leaves behind…

A

a concave, crescent-shaped scar and a convex lobe below.

58
Q

Mudflow is similar to…

A

earthflow, but has thinner consistency due to high water content and it is more rapid.

59
Q

Cause of mud flow is…

A

combination of high rainfall or snowmelt, often with impermeable rock layer beneath.

60
Q

Mudflow is common in…

A

mountainous regions after heavy rainfall, periglacial areas ar the summer thaw maximum or on the slopes of erupting volcanoes(lahar flow).

61
Q

A speed of a heave/creep is…

A

0.1mm to 1cm a year

62
Q

A speed of solifluction is…

A

1cm a year to 1mm a day

63
Q

A speed of landslide is…

A

around 1 m a day on average.

64
Q

A speed of earth flow or mudflow is…

A

1m a day to 1m per second

65
Q

A speed of debris avalanche is…

A

1 m/s to 360km/h

66
Q

A mud/earth flow forms…

A

toe-fans out at the base, usually made of very fine clay.

67
Q

Type of mass movements are:

A
  • flows
  • slides
  • slumps
68
Q

Rotational slides produce…

A

a series of massive steps or terraces.

69
Q

Slides often occur when there is…

A

a combination of weak rocks, steep slopes and active undercutting.

70
Q

Slides are triggered by…

A

change in water content or by very cold conditions.

Physical Geography A-level (33 decks)

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